1. Field of the Invention
The present invention relates to a progressive die assembly and a method for manufacturing lamina stacks from a plurality of separate strips of stock material.
2. Description of the Related Art
The manufacture of parts, e.g., stators and rotors for electric motors, ignition assembly cores, or other parts which employ stacked laminas is well known in the art. Typically, the laminas are blanked from a continuous strip of stock material and are then stacked and bound together to form the completed part. Progressive die assemblies for producing lamina stacks, wherein a strip of lamina material is fed through a sequence of punching steps to progressively form the laminas to the desired end configurations, are also well known.
One type of lamina stack, for example, includes a plurality of individual layers of stacked laminas, wherein some of the laminas are made from a first type of material and others of the laminas are made from a second, different type of material. The laminas of the different materials are attached to one another in a suitable manner such as by binding the entire stack together with a cleat. For example, one such lamina stack may include a first portion, or first set, of lamina layers made from a first type of metal, and a second portion, or second set, of lamina layers made from a second type of metal.
Problematically, known progressive die assemblies are configured to stamp laminas from only a single strip of stock material which is fed into the die, wherein the individual laminas are progressively shaped by punches in the die and are thereafter blanked or separated from the remainder of the strip and then stacked in a choke assembly. One of ordinary skill in the art would readily recognize that changing the type of stock material which is fed into the die to manufacture the respective layers or portions of each lamina stack would be extremely inefficient, if not impossible.
Another potential method of manufacturing the foregoing types of lamina stacks would be to use two separate progressive die assemblies, one die assembly forming first portions or first sets of lamina layers of the stacks from strips of a first material, such as a first type of metal, and a second die assembly forming second portions or second sets of lamina layers of the stacks from strips of a second material, such as a second type of metal. Thereafter, to form each stack, a first portion may be manually secured to a second portion, such as by using a cleat which is applied by a manually-actuated hand press, for example. A disadvantage with the foregoing method is that same requires a manual step for the assembly of each lamination stack, thereby leading to production inefficiencies when very large numbers of stacks are produced. The foregoing method is particularly inefficient where the lamina stacks include several interleaved layers of laminas made from different materials.
What is needed is a die assembly and method which is an improvement over the foregoing.